Math notation on WordPress.com?

I am a new user with WordPress, and I would like to use mathematical formulas. I have been reading the mathjax pages for hours, such as this one and quite a few others. This may be a bad question, but can someone please help me? All I want to do is enable Latex, and I am hopelessly lost. My most recent attempts have been trying to find the “header file” so that I can copy and paste in